The analysis of a biological sample such as a clinical sample or a test sample of food, for presence of a pathogen such as a virus, or to determine the presence of a particular gene, will typically include detecting one or more polynucleotides present in the sample. One type of detection is qualitative detection, which relates to a determination of the presence or absence of a target polynucleotide and/or the determination of information related to, for example, the type, size, presence or absence of mutations, and/or the sequence of the target polynucleotide. Another type of detection is quantitative detection, which relates to a determination of the amount of a particular polynucleotide present in the sample, expressed for example as a concentration or as an absolute amount by weight or volume. Detection may also include both qualitative and quantitative aspects. Quantitative detection is typically, however, a more challenging pursuit than is a simple qualitative determination of presence or absence of a polynucleotide.
Detecting polynucleotides often involves the use of an enzyme. For example, some detection methods include polynucleotide amplification by polymerase chain reaction (PCR) or a related amplification technique. Other detection methods that do not amplify the polynucleotide to be detected also make use of enzymes. However, the functioning of enzymes used in such techniques may be inhibited by the presence of materials (known as inhibitors) that accompany the polynucleotide in many biological—particularly clinical—samples. The inhibitors may interfere with, for example, the efficiency and/or the specificity of the enzymes.
Polynucleotide detection today is moving towards ever more rapid, and ever more sensitive techniques. For example, rapid and accurate diagnosis of viral infections is invaluable for accurate patient management by directing the administration of appropriate antiviral therapy, eliminating the unnecessary utilization of antibiotics and monitoring individual response to the prescribed regimen. Given its significant advantages of sensitivity, specificity and time to result, polynucleotide detection (or nucleic acid testing) has become the presumptive international standard for viral diagnosis.
However, the application of nucleic acid testing to routine diagnosis of viral targets has been limited to large clinical reference labs and major hospital labs due to the high cost, complexity and skill level requirements for implementing such testing. While significant improvements have been made in recent years, the successful detection of RNA viruses in particular requires extremely laborious extraction procedures frequently relying on the use of toxic chemicals. Furthermore, RNA molecules can be very unstable and hence can require delicate processing/handling during their determination. These issues to date have been overcome with the use of large, expensive, time consuming robotic equipment.
With the current demands on practice of medicine, laboratories that carry out diagnostic testing on patient samples see substantial benefits from having extremely high throughput, which in itself is assisted if the time to arrive at a diagnostic outcome for a given sample is made as short as possible. Testing may also be made more rapid if the actual sample on which the tests are run is made as small as possible. More recently, there has been a growing need for a small, easy to use, low-cost, automated platform for the extraction of high quality RNA from viral targets in clinical specimens.
Correspondingly, then, the need to be able to isolate minute quantities of polynucleotides from complex biological samples in a manner that effectively avoids the presence of, or reduces the detrimental impact of, inhibitors is ever more important. Furthermore, given the availability of various stand-alone automated amplification apparatuses, it is desirable to be able to routinely and reliably extract from a raw clinical sample a quantity of polynucleotide that is ready—in terms of purity and quantity—for amplification.
The discussion of the background herein is included to explain the context of the technology. This is not to be taken as an admission that any of the material referred to was published, known, or part of the common general knowledge as at the priority date of any of the claims found appended hereto.
Throughout the description and claims of the specification the word “comprise” and variations thereof, such as “comprising” and “comprises”, is not intended to exclude other additives, components, integers or steps.